Ignition device for mercury arcs



Feb. 2, 193 J. VON ISSENDORFF ET AL 1,343,654

IGNITION DEVICE FOR MERCURY ARCS Filed Jan. 19, 1927 INVENTOR5 l/fgen [amiss enaqri aad/ /exgaclklmgmlc ATTORNEY WITNESSES:

Patented Feb. 2, 1932 UNITED STATES J'U'RGEN VON IS SENIDORFF, OF BERLIN-SIEMENSSTADT, AND HEINRICH JUNGMIOHL, OF

NEU-FINKENKRUG, NEAR SPANDAU, GERMANY, ASSIGNORS TO WESTINGHOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA IGNITION DEVICE FOR MERCURY ARCS Application filed January 19, 1927, Serial No. 162,076, and in Germany January 27, 1926.

Our invention relates to arc-discharge apparatus and particularly to such apparatus having at least one liquid electrode.

The principal object ofour invention is to 5 provide means for starting an are between a liquid electrode and another electrode when such electrodes are inaccessible to purely mechanical means for imparting relative motion thereto, as, for example, when they are 10- 10 catedinside an enclosing vessel which must be kept vacuum-tight.

Mercury-arc rectifiers afford examples of the type mentioned and it is the present practice to initiate current-flow therein by tilting the containing tube bodily until an auxiliary anode makes contact with the mercury of the cathode. Upon restoring the tube to its normal position, thereby breaking the contact, an arc is drawn between the electrodes. In the case of rectifiers of small or medium size this tilting process causes no great difficulty, but,'-in units of large-size, the weight of mercury is considerable, and it is difiicult to so support the tube that it will not be broken under the impacts and stresses involved in tilting it. By the use of one embodiment of our invention, which we illustrate herein, the difiiculty just mentioned is entirely avoided since tilting of the container to start the arc becomes unnecessary. We accomplish starting of the are by causing a part of the electrode liquid to be expelled, as a -jet,'through an orifice and so directing this jet that, for a moment, it impinges upon another electrode. Upon cessation of the flow of the jet, an arc is drawn between the electrodes in question. Further objects accomplished by our invention will become apparent upon reading the following specification.

With such objects in view,'our invention comprises the methods and structural arrangements hereinafter described, claimed and illustrated in the accompanying drawing wherein the single figure is a sectional view of a portionof a mercury-arc tube and its anode and cathode provided with means, shown diagrammatically, for starting an are between the electrodes.

In the drawing, the reference character 1 designates the containing vessel, which may be of glass, and of which only the portion in the vicinity of the cathode is shown.

The liquid electrode 2, which is ordinarily mercury, is contained in a reservoir 3 forming the lower end of the arc tube 1. A metallic lead 4 is sealed through the container wall, in a manner well-known in the art, and, through this lead, current may flow from the electrode 2 to an external electrical circuit. A second electrode 5, which may be of graphite is supported slightly above the surface of the liquid electrode 2 by a conductor 6 which is also sealed through the container wall. All the foregoing is a common arrangement of the.so-called side-branch or exciting arc in mercury-arc rectifiers.

A source of electromotive force 7, provided with a suitable control resistor 8, is connected between leads 4 and 6, and when, by any means, contact is made between electrodes 2 and 5 and is then interrupted, an arc will be drawn between them.

As has already been stated, it is the present practice to bring about contact between electrodes 2 and 5 by tilting the arc tube bodily until the liquid 2.fiows into contact with electrode 5 and then to return the tube to its normal position, as illustrated here. In tilting tubes of larger size the heavy mercury may cause such strains as to result in breakage of the containing vessel.

' In accordance with our invention, to avoid all necessity for so tilting the container, we provide the main chamber 3 of the cathode reservoir with an auxiliary chamber in the form of a U-shaped tube 9, the outer end of which rises to a point higher than the level of the surface of the body of mercury 2. Between the main chamber 3 and the auxiliary chamber 9 we arrange the separating partition 10 provided with a nozzle the orifice of which projects to a point just beneath the surface of the liquid 2.

In the outer end of the auxiliary chamber 9 we place an iron cylinder 12 which floats on the surface of the mercury therein. Upon the outer arm of the U-shaped tube 9 we place a solenoid 13 which may be energized by current from a source 14 of electromotive force, in series with which is connected an approtit) priate resistor 15. When we desire to strike an are between electrodes 5 and 2 We can, by closing a switch 16, which controls the circuit of the solenoid 13, energize the latter, which is so positioned as to exert a downward pull on the iron member 12. As a result, the hydrostatic'pressure in the auxiliary chamber 9 is increased. A jet of liquid is thereby expelled from the nozzle 13 and the latter is so positioned that this jet strikes electrode 5 to complete a circuit between electrodes 5 and 2. The out-flow of liquid from the nozzle 11 relieves the pressure in the auxiliary chamber 9 and, as a result, the jet above mentioned gradually subsides and disapears. In so subsiding the jet draws an are between electrodes 5 and 2, and, once struck, this are will continue to operate for an indefinite time.

With such a side are between electrodes 5 and 2 in operation, arcs between electrode 2 and other electrodes in the containing vessel will start spontaneously, upon a proper application of electromotive force thereto, as is well-known.

It may be noted that the nozzle 11 may be so directed that the jet it expels does not impinge upon the wall of the containing Vessel. This is an important advantage, in the case of glass mercury-arc tubes, for the reason that the glass walls above the level of the mercury cathode become, during operation, considerably hotter than the mercury itself. If, for any reason, the arc is shut 01f and it is desired to immediately restart it, much trouble arises with the present method of starting by tilting the arc tube, since cold mercury, striking the hot tube walls, often causes the glass thereof to crack, thus ruining the tube forthwith. With our arrangement, this difliculty also is avoided.

While we have illustrated. our invention as applied to an arc comprising one mercury and one solid electrode, it is obviously not limited to that particular liquid nor to a solid second electrode. Neither is the location of the electrodes in the vacuum-tight container the only sort of inaccessibility to mechanical operation that renders our invention useful. Moreover, it is clear that the projected liquid need not be the only constituent of either electrode, since it is used only temporarily. -We contemplate, as well, the broad idea of drawing an are between two electrodes by temporarily bridging the gap between them by a jet of conducting liquid.

Various improvements and modifications of the arrangement which has been described above for producing the liquid jet, and other modifications of details of embodiment of our invention will be apparent to those skilled in the arts, and it is ourdesire that only such limitations shall he placed upon our inven tion as are indicated in the appended claims or are imposed by the prior art.

eaaeee We claim as our invention:

1. In an arc-discharge apparatus, a menuIn-tight container, one electrode com rising a fluid, a second electrode,a reservoir or said fluid electrode comprising a main chamber and an auxiliary chamber separated by a stationary dividing partition, an orifice in said partition connecting said chambers, and means to subject the fluid in said auxiliary chamber to a substantially constant pressure, said orifice being so positioned as to cause a jet of fluid to flow therethrough and to impinge upon said electrode.

2. In an arc-discharge device, avacuumtight container, a fluid electrode, a second electrode, a U-shaped reservoir for said fluid electrode comprising a main chamber and an auxiliary chamber separated by a partition having an orifice provided with a nozzle directed towards said second electrode, an iron plunger in the auxiliary chamber adapted to be partly submerged in said liquid, and

magnetic means for changing the amount of such submergence.

3. In an arc-discharge apparatus, a vacuum-tight container, a mercury electrode, a second electrode, a U-shaped reservoir for said mercury electrode comprising a main chamber and an auxiliary chamber separated by a partition pierced by an orifice having a nozzle, an iron plunger floating on the mercury in said auxiliary chamber, and magnetic means to exert a force on said plunger, said nozzle being so directed as to cause a jet of mercury to impinge upon said second electrode.

In testimony whereof, we have hereunto subscribed our names this 20th day of December, 1926.

JURGEN VON ISSENDORFF. HEINRICH JUNGMICHL. 

